This invention relates generally to a portable system for testing electrical circuits and more specifically to a system which prevents interruption in circuit function during testing.
Normally, testing electric circuits is a relatively simple task. However, in a case where the circuit is formed on a board and the board is a part of a larger system which cannot be practically shut down, the problem becomes more difficult. Those which cause particular difficulty are electronic alarm security systems. These systems include a number of sensing units placed at strategic locations around an area or within a building. All sensors would be connected to a master security panel located in a security office on or off the premises. The advantage to such a system is easily seen where one person can monitor a large panel containing substantial numbers of alarms with a single glance.
Operation of security systems is simple, with a light and/or an audible alarm being activated by the remote sensing detector. Means are provided to allow access without activating the sensor and means are provided to reset the alarm once it has been activated.
Maintenance and repair of the system is far more complex and sensitive than the operation. Since there are usually a number of sensors to any system, there will be a corresponding number of alarm modules mounted, usually in a unified master panel for ease in monitoring. When one module needs maintenance, the particular sensor connected to it has to be shut down. Additionally, as a practical matter, maintenance personnel working around a master security panel tend to disrupt operations, block the panel from the view of security people and tend to cause alarm indications which are attributed to maintenance, thereby masking true alarms.
A typical security system is manufactured by the American District Telegraph Co (ADT) model 5930-018. This system utilizes readout modules in the master panel which are the supervisory and control elements of the alarm system. The readout module consists of a front plate which mounts in the master panel. This plate contains lights for indicating an alarm visually and switches for setting or resetting the alarm system. An audio alarm is also a part of the master panel.
Transverse to the front plate is a circuit board which is hidden behind the front panel when mounted in master panel. The circuit board contains all the necessary circuitry to cause the system to function and contains a plug-in feature whereby readout modules are simply plugged into the master panel.
Readout modules must be periodically checked and readjusted due to changes in temperature, age and line voltage. Occasionally, a malfunction in the system will require that the module be examined for defects.
Currently available maintenance equipment for testing readout modules is difficult to use, particularly in cramped quarters where master panels tend to be located. They contain meters that are difficult to read and their use tends to cause the master panel to be obscured either in whole or in part. Additionally, existing equipment causes the master panel audio alarm signal to function during testing thereby possibly allowing a working active module to be inadvertently compromised.
Additionally, there is no means for bench testing readout modules short of inserting them into an active system. Similarly, there is no way of training personnel on the maintenance of these systems modules except by utilizing an active alarm system.
The invention proposed herein solves the outlined short comings of existing alarm systems.